Viscose solution, a process for making it and a filament formed from it



United VISCOSE SOLUTION, A PROCESS FOR MAKING IT AND A FEAIVIENT FQRMED FROM IT N Drawing. Application November 8, 1952, Serial No. 319,604

18 Claims. (Cl. 106-465) This invention relates to the production of viscose, and more particularly relates to the production of viscose of improved clarity.

As is well known, the usual viscose solution employed in the production of shaped materials such as filaments, films, foils and the like, is normally cloudy and contains appreciable amounts of suspended material. This suspended material tends to clog the filters employed prior to the extrusion of the viscose solution, to deposit on the spinning jets, thus reducing their dimensions and making spinning uneven, to form pits and points at which viscose skins can form on other parts of the spinning apparatus, and to form agglomerates in the spun yarn itself. It has been proposed to improve the clarity of the viscose solution by the addition thereto of various sulfonated fats, oils or fatty acids. Although some improvement has been obtained by this expedient, the resulting viscose solution is still cloudy and forms undesirable deposits on filters, spinning jets and other parts of the apparatus.

An object of this invention is a process of producing clarified viscose solution which will be substantially free from the foregoing and other disadvantages.

A further object of this invention is the provision of a novel filamentary material produced by spinning process wherein a clarified viscose solution is employed.

Other objects of this invention will be apparent from the following detailed description and claims.

According to this invention, the clarity of the viscose solution is greatly improved by incorporating therein a small amount of a sodium salt of an aldohexonic acid, preferably a sodium salt of gluconic acid. The term aldohexonic acid, as employed herein, denotes those acids having the formula HOCH2(CHOH)4-COOH, such as gluconic, talonic, galactonic, idonic, gulonic, mannonic, altronic and allonic acids, in both their dextro and levo forms. The sodium salt of the aldohexonic acid not be added as such, but may be incorporated into the viscose solution by adding certain other aldohexonic compounds. For example, we may add an aldohexonic acid or a lactone of an aldohexonic acid to the viscose solution or to a component Which enters into the viscose solution. Since a viscose solution contains an excess of sodium hydroxide, the acid or the lactone is converted into the corresponding sodium salt in the viscose solution. The sodium salt of the aldohexonic acid may also be incorporated into the viscose solution by adding another alkali metal salt of the aldohexonic acid, for example a potassium salt of the aldohexonic acid, e. g. potassium pluconate. When such other salts are added, the sodium ion present in overwhelming predominance in the viscose solution displaces the other alkali metal ion by metathesis until equilibrium concentrations of the two alkali metal ions and their corresponding aldohexonic acid salts are obtained. Aldohexonate salts which introduce objectionable ions into the viscose solution, such as barium, calcium, manganese, zinc, iron, lead or copper salts, should be avoided, since the metal ions of such salts react in the Patent 0 2,770,554 Patented Nov. 13, 1956 viscose solution to form objectionable precipitates, such as oxides, hydroxides or hydrated oxides.

While the aldohexonic compound may be added at any stage in the preparation of the viscose solution, it has been found that the optimum results are obtained when the aldohexonic compound is added at the earliest practical point. For example, the aldohexonic compound may be added to the caustic soda used for steeping the cellulose in making alkali cellulose, but this introduces some practical difiiculties in analyzing for the aldohexonate and maintaining a desirable aldohexonate content of the viscose solution, since part of the caustic soda used for steeping is recirculated. The aldohexonic compound may also be added to the alkali cellulose just before or during the shredding operation, or in the aqueous sodium hydroxide used to dissolve the cellulose xanthate., or to the viscose solution itself, preferably before the ripening step, or at any other suitable point in the process. The aldohexonic compound may also be added in increments; for example, part may be added before the shredding of the alkali cellulose and part to the caustic soda used for dissolving the cellulose xanthate.

Although the proportions of the aldohexonic compound may be varied widely, we prefer to employ amounts yielding from about 0.0025 to about 0.020%, based on the Weight of the viscose solution, of aldohexonate radical.

The aldohexonic compound need not be the only clarifying agent present in the viscose solution. It is often desirable to add to the viscose solution both an aldohexonic compound and a sulfated fat, oil or fatty acid clarifying agent, such as disclosed in U. S. Patents Nos. 1,925,- 192 and 1,936,479. In such cases, the proportions of the two clarifying agents may be varied widely. For example, the viscose solution may be clarified by the addition thereto of 0.005% of gluconic acid and 0.020% of a highly sulfated oleic acid, both proportions based on the Weight of the viscose solutions. A suitable source of the sulfonated oil is Prestabit Oil-V-New,. a 50% aqueous solution of a sodium salt of highly sulfated oleic acid from which any lower substituted material has been removed, sold by General Dyestufi Corporation.

In order further to illustrate our invention, but without being limited thereto, the following examples are given:

Example I A viscose solution having a cellulose content of about 8% is prepared in the usual manner by adding aqueous caustic soda to cellulose xanthate in a mixer. Varying proportions of a 5% solution of gluconic acid in water are added to one batch of this viscose solution during the mixing operation. These proportions provide 0.005% to 0.030% of gluconate radical based on the total amount of viscose solution. Similar proportions of a 5% solution of a conventional viscose clarifier, namely, a sodium salt of highly sulfated oleic acid, are added to another batch of the same viscose solution during the mixing operation. These proportions provide 0.005% to 0.030% of the sodium salt of highly sulfated oleic acid, based on the total amount of viscose solution. By measurement with a colorimeter, it is found that all of the samples of viscose solution treated With gluconic acid transmit 2.5 times asv much light as unclarified viscose solution. In contrast, the maximum, light transmission obtained with the .salt of sulfated oleic acidis only 1.25 times the light transmission of unclarified viscose solution, and this maximum effect is not obtai ned until the concentration of thesalt of sulfated oleic acid in the viscose solution is 0.015%, based on the total amount of viscose solution. 5

All these samples of viscose solution are formed into yarns in the usual manner by extrusion through spinning jets into conventional coagulating baths containing sulfuric acid. The resulting yarns are substantially identical in hand, cross-section and physical properties. The yarn spun from the viscose solution containing the gluconic acid is slightly lighter in color and clearer than the yarn spun from the viscose solution containing the salt of sulfated'oleic acid, which in turn is much lighter and clearer than the yarn spun from the unclarified viscose solution.

Example I! Ten equal batches of shredded alkali collulose are prepared by steeping and shredding in the usual manner. During the shredding operation, the salt of sulfated oleic acid used in Example I is added to 5 batches and gluconic acid is added to the other 5 batches. These clarifying agents are added as aqueous solutions thereof in admixture with the steep soda solution commonly used to adjust the composition of the alkali cellulose to compensate for small natural variations in the press ratio of the alkali cellulose. Each of the alkali cellulose batches is then converted to viscose by ageing, xanthating, and mixing with aqueous caustic soda in the conventional manner, and is ripened by passing it through the usual ripening tanks and filter presses. The final batches of viscose solution, having a cellulose content of about 8%, contain 0.020% of salt of sulfated oleic acid or 0.010% of gluconate radical, based on the total weight of the viscose solution.

At the termination of the viscose mixing (or cellulose xanthate dissolving) period, the batches of viscose (unripened and unfiltered) made with the salt of sulfated oleic acid have an average count of 238 microscopic fiber particles greater than 50 microns in length per cubic centimeter of viscose and contain a number of long undissolved or incompletely dissolved fiber particles which are visible to the naked eye but above microsopic size range and are not normally included in a conventional microscopical fiber count. These batches of viscose show an average light transmission to incandescent light of only 21% based on a standard of 100% light transmission for distilled water. In contrast, the corresponding batches of viscose solution made with gluconic acid have a corresponding particle count of only 144, contain a relatively much smaller number of fiber particles above the microscopic size range and show a corresponding light transmission of 48%. After the filtering operation, it is found that the filter dressings used for the viscose solution clarified with gluconic acid are much cleaner than those used for the viscose clarified with salt of sulfated oleic acid.

Substitution of glucono delta lactone for gluconic acid on an equimolar basis in Examples I and 11 gives substantially identical results.

It is to be understood that the foregoing detailed description is given merely by way of illustration and that many variations may be made therein without departing from the spirit of our invention.

Having described our invention, what we desire to secure by Letters Patent is:

1. In the process for the production of viscose solutions for the manufacture of shaped materials, the improvement which comprises adding to the viscose solution, at any stage in its manufacture, an aldohexonic compound selected from the group consisting of aldohexonic acids, alkali metal salts of aldohexonic acids and aldohexonic lactones.

2. In the process for the production of viscose solutions for the manufacture of shaped materials, the improvement which comprises adding to the viscose soluj tion, at any stage in its manufacture before it is fully ripv ened, an aldohexonic compound selected from'the group provement which comprises adding to the viscose solution, at any stage in its manufacture, an aldohexonic compound selected from the group consisting of aldohexonic acids, alkali metal salts of aldohexonic acids and aldohexonic lactones, the amount of said aldohexonic compound providing about 0.0025 to about 0.020% of aldohexonate radical based on the weight of the viscose solution.

4. in the process for the production of viscose solutions for the manufacture of shaped materials, the im provement which comprises adding to the viscose solution, at any stage in its manufacture before it is fully ripened, an aldohexonic compound selected from the group consisting of aldohexonic acids, alkali metal salts of aldohexonic acids and aldohexonic lactones, the amount of said aldohexonic compound providing about 0.0025 to about 0.020% of aldohexonate radical based on the weight of the viscose solution.

5. In the process for the production of viscose solutions for the manufacture of shaped materials, the improvement which comprises adding gluconic acid to the viscose at any stage in its manufacture, the amount of gluconic acid being suflicient to improve the clarity of the viscose.

6. In the process for the production of viscose solutions for the manufacture of shaped materials, the improvement which comprises adding glucono lactone to the viscose at any stage in its manufacture, the amount of glucono lactone being sufiicient to improve the clarity of the viscose.

7. In the process for the production of viscose solu tions for the manufacture of shaped materials, the improvement which comprises incorporating sodium gluconate into the viscose in order to improve the clarity of the viscose.

8. In the process for the production of viscose solutions for the manufacture of shaped materials, the improvement which comprises adding to the viscose, at any stage in its manufacture, a clarifying agent selected from the group consisting of aldohexonic acids, alkali metal salts of aldohexonic acids and aldohexonic lactones and a clarifying agent selected from the group consisting of sulfated fats and sulfated fatty oils.

9. in the process for the production of viscose solutions for the manufactureof shaped materials, the improvement which comprises adding to the viscose solution, at any stage in its manufacture, a clarifying agent which is an aldohexonic compound selected from the group consisting of aldohexonic acids, alkali metal salts of aldohexonic acids and aldohexonic lactones and a clarifying agent which is a sulfated fatty acid.

10. In the process for the production of viscose solutions for the manufacture of shaped materials, the improvement which comprises adding to the viscose, at any stage in its manufacture, a clarifying agent selected from the group consisting of aldohexonic acids, alkali metal salts of aldohexonic acids and aldohexonic lactones and a sulfated oleic acid clarifying agent.

11. In the process for the production of viscose solutions for the manufacture of shaped materials, the improvement which comprises adding to the viscose, at any stage in its manufacture before it is fully ripened, a clarifying agent selected from the group consisting of aldohexonic acids, alkali metal salts of aldohexonic acids and aldohexonic lactones and a sulfated oleic acid clarifying agent.

12. A viscose solution containing a sodium aldohexonate in an amount sufiicient to improve its clarity.

13. A viscose solution containing sodium gluconate in an amount sufficient to improve its clarity.

14.. A viscose solution containing sodium gluconate in an amount sufficient to improve its clarity, said solution containing about 0.0025 to about 0.020% of gluconate radical.

15. A viscose solution containing a sodium aldohex onate in an amount sufficient to improve its clarity and containing, as an additional clarifying agent, a sodium salt of a sulfated fatty acid.

16. A viscose solution containing sodium gluconate in an amount sufiicient to improve its clarity and containing, as an additional clarifying agent, a sodium salt of sulfated oleic acid.

17. A filament produced by extruding in filamentary form a viscose solution containing a sodium salt of an aldohexonic acid in amount sufficient to improve its clarity into a coagulating bath containing sulfuric acid.

18. A filament produced by extruding in filamentary form a viscose solution containing sodium gluconate into a coagulating bath containing sulfuric acid.

References Cited in the file of this patent UNITED STATES PATENTS Koch Sept. 5, 1933 Koch Nov. 21, 1933 FOREIGN PATENTS France Mar. 26, 1952 Great Britain 1908 Austria Aug. 10, 1901 France Aug. 29, 1927 France Apr. 11, 1939 Germany Aug. 7, 1930 

12. A VISCOSE SOLUTION CONTAINING A SODIUM ALDOHEXONATE IN AN AMOUNT SUFFICIENT TO IMPROVE ITS CLARITY. 